Provided in this type of telephone set is, generally, a security function (described as a locking function hereinafter) with which the telephone set is disabled to be used unless a correct identification number is inputted thereinto to prevent any person other than an authorized owner of the telephone set from using it without authorization. Namely, the locking function is unlocked in response to input of the correct identification number thereinto.
As a conventional technology relating to this type of locking function, there is Japanese Patent Laid-Open Publication No. SHO 61-236226. In this Publication, there is disclosed a technology that calls are transmitted from a mobile telephone set or received thereby by inputting an identification number thereto at the time of using the mobile telephone set and obtaining identification by collating it to the identification number previously stored therein.
There has been proposed a telephone set in which a security function is provided so that a particular number such as a telephone number for a long-distance call or the like (described as a call-restricting function hereinafter) is restricted. In this case, the call-restricting function is also unlocked in response to input of a correct identification number thereinto.
In the conventional type of telephone set as disclosed in the publication, unlocking of a locking function and a call-restricting function is first set according to input of an identification number and call setting is carried out, which makes the operations complicated.
After the call is unlocked, and when prevention of unauthorized use of a telephone set or a restriction of particular numbers are also required for the next use thereof, the locking function and the call-restricting function are necessary to be set again, which makes the setting of a security function therein troublesome.